The dusty sagebrush desert makes a perfect backdrop for the more than 75 participants who get gussied up in 19th century costume to socialize and compete in Cowboy Action Shooting, a fantasy sport that combines a heap of historical flavor with rapid-fire target shooting.

For a few hours a month, ordinary people become steely eyed lawmen or bad-news drifters. At least in their own minds, they become Jesse James or Wyatt Earp, or Annie Oakley or Belle Star.

''This is a chance to do what I was doing when I was 10 or 11 years old out in my backyard only now I can do it with real guns,'' said Ray Walters, a 55-year-old former firefighter who now writes for the Boise-based SHOOT! magazine.

The competition, governed by the Single Action Shooting Society, has existed since the early 1980s. There are numerous styles of match competition, from mounted pistol shooting to short-range derringer competitions to long-range rifle shoots. Most common are medium-range pistol, rifle and shotgunning games.

Matches are divided into eight or 10 scenarios, called ''stages.'' Shooters fire through a doorway, around a corner or out of a window at steel squares, circles or small cowboy silhouettes from 5 to 15 yards away. They use multiple combinations of pistols, rifles and shotguns. Sometimes an extra element is added, such as throwing a knife or hatchet into a target.

A timer keeps electronic track of how long it takes a competitor to shoot through the stage which usually lasts less than a minute. Official observers watch for safety violations, gun handling problems and target misses, which can add time to the overall score.

Cowboy shooters are assigned aliases, which they prefer to their real names during competitions. Walters is ''Smith n' Jones.'' Deana Daniels is ''Missy Marble.''

''Yeah, but they call me 'Hagatha' when I miss,'' a frustrated Daniels said after hitting 10 pistol shots, 10 rifle shots but missing one of five shotgun blasts all in 38.9 seconds.

Competition is friendly because there's no prize or cash award winners just bragging rights and belt buckles. But even at that, devoted shooters practice hours a day.

''There's no pressure in cowboy action, you compete against yourself,'' Graham said.

Dan Lopez is a 37-year-old nurse from Adrian, Ore. When he straps on his belt and guns, he becomes Sancho Ponza, a dashing desperado with a red sash, a black goatee and a long cigar.

Lopez is good. Real good, for just his third year in the game. His compadres say he's got the quickest gun and steadiest hand of all in the Oregon Trails chapter. He travels a few times a year to regional competitions and has his sights set on the nationals.

His performance secrets include good health, lean muscles and hundreds of hours of practice. It's not uncommon for serious cowboy shooters to fire 700 to 800 bullets a week.

''You've got to be comfortable with what you are doing. Plus, we have a lot of friends and we all learn from each other,'' he said.

Just like in the Old West, women are toting guns at the matches just like the menfolk. Sharon Wright, who shoots as ''Six-gun Sam,'' has won two state championships. Before she got involved four years ago, she had never fired a gun.

Participation by women ''makes for a lot more harmony to get the wife or girlfriend out,'' Wright said.

You can spot a greenhorn in this sport a mile away. Beginners wear a stiff cowboy hat and gun belt over jeans and sneakers. Old-timers who have spent some cash over the years have invested in chaps, scarfs, fancy satin vests, pocket watches, spurs and leather cuffs.

Women sometimes make their own Victorian-era dresses.

''When I first started, I was not wild about the outfits,'' said Brian D. Graham, a.k.a. ''Doc Graham, the Oregon Trail chapter president.

''Once you get into it, you find yourself always trying to find just the right cowboy hat and just the right cowboy boots that make you feel good.''

The sport can get expensive. Ada County Sheriff's Deputy Brenda Glenn, who goes by ''Dakota Star,'' sports a custom-made gun belt and holsters that cost $1,500, including engraved American Indian artwork.

Some participants really aren't in it for the competition or the precise historic dress. They just want to have fun.

And that's why Ryan Groves, an electronics professor at the College of Southern Idaho, showed up to one shooting match with a black mortar board on his head and sporting a full academic robe usually only worn by professors at graduation ceremonies.

Groves goes by the cowboy handle, ''Irving, the 142nd Fastest Gun in the West.'' He gleefully blasted away with is huge original 1887 black powder 10-gauge through the day's stages.

''You get a lot of bang and boom and smoke,'' Groves said, his eyes twinkling from his performance.

The entire field stopped briefly and chuckled at Grove's thundercloud.

''He should get points just for the percussion value,'' one of the officials commented. ''Next shooter up.''